Figure 7.

pH dependence of the helical stiffness of the D27H/E28H double mutant of the Ψ-WT SAH domain of myosin VI, paramagnetically tagged at I13C. (A) Shown here is the ¹H^N chemical shift titration of H27 (yellow) and H28 (magenta), with the solid lines representing the best fits to the Henderson-Hasselbalch equation. (B) RDC versus residue number in the Ψ-WT (black) and D27H/E28H mutants at pH 7.5 (blue) and pH 5.5 (red) is shown here. Solid lines correspond to the best-fitted dipolar wave patterns (28) for residues R24–E62, multiplied by a decaying exponential function with a decay constant of 49.75 residues. For the D27H/E28H mutants, only RDCs for residues R30–E62 were included in the dipolar wave fit; continuation of the dipolar wave in the N-terminal direction is depicted by dashed lines. The arrow marks the location of the paramagnetic tag. (C) The correlation between ¹D_NH RDCs of residues R30–E68 in the D27H/E28H double mutant and Ψ-WT at pH 7.5 (blue, slope 0.74; R² = 0.985) and pH 5.5 (slope 0.47; R² = 0.976) is shown here. To see this figure in color, go online.